The present invention relates to a developer which visualizes an electrostatic latent image on an image carrier, and an image formation apparatus, such as a copier, a printer or a facsimile, which has the developer.
A high temperature fixing device is provided in an image formation apparatus. With laser exposure, an exposure section (optical writing unit) in the image formation apparatus includes a polygon motor which rotates at high rate and serves as a heat emission source which generates a large amount of heat. Even with LED exposure, a light source generates a large amount of heat. In such an environment, a developer has a mechanism of stirring and transporting a developing material and serving as one of a heat emission sources although the developer is smaller in heat emission quantity than the fixing device and the exposure section.
If an image formation rate is accelerated, it is necessary to stir and transport the developing material at high rate, as well. This is because it is necessary to secure the quantity of the developing material carried by a developing material carrier and for a developer which employs a two-component developing material to stabilize the quantity of toner in the developing material. If a developing material stirring and transporting member, such as a paddle or a screw, in a developing material container is driven at high rate, frictional heat is generated to heat the developing material and to easily deteriorate the developing material. This causes the temperature rise of the developer and also of image formation devices around the developer, thereby producing disadvantages in the operation or image quality of the image formation apparatus.
The ordinary configuration of an image formation apparatus intended to suppress the temperature rise of a developer is such that aluminum or the like having high heat conductivity is used as the material of a casing and an air flow is generated on the outer wall of the casing to thereby accelerate heat exchange. In addition, many apparatuses have been proposed (see, for example, Japanese Patent Application Laid-Open No. 5-188754) each of which air-cools the outside of a developing material container so as to suppress the temperature rise of the developer. To efficiently cool the developing material in the developing material container, in particular, it is effective to cool the bottom of the developing material container which is large in an contact area with the developing material.
At present, there is known, as an image formation apparatus which can form multicolor images, a tandem type image formation apparatus which can output images at a higher rate than that of a revolver type image formation apparatus or a juxtaposition type image formation apparatus since the tandem type image formation apparatus does not perform a color switching operation. However, the tandem type image formation apparatus requires an image carrier for each color, leading to the result that the entire apparatus becomes large in size. To suppress the apparatus from being made large in size, the tandem type image formation apparatus is required to make each image formation unit small in size and to increase the density of the units.
With the configuration of the image formation apparatus intended to suppress the temperature rise of the developer by using a member having high heat conductivity as the casing, if a fixing device is disposed right under the developer or constituent members are crowded, the temperature of the surrounding of the developer is higher than that of the developer, which often makes the developer become a heat receiving side. In addition, if the members are crowded, it is difficult to secure a space which functions as a channel for generating an air flow to suppress temperature rise.
With the configuration of air-cooling the outside of the developing material container, it is difficult to provide a device which directly cools the developing material container in proximity to the developer. In addition, a transfer device which transfers a toner image on a photosensitive drum to a transfer body or an intermediate transfer body and a transport path for the transfer body or the intermediate transfer body are arranged around the photosensitive drum downstream of the developer. Therefore, there is no spatial room for the provision of a cooling unit. According to the conventional art, therefore, it is difficult to sufficiently suppress the temperature rise of the developer in an image formation apparatus, such as the tandem type image formation apparatus, in which constituent members are crowded.
It is an object of the present invention to provide a developer which can cool the developing material container of the developer irrespective of the outside temperature of the developer even if there is no spatial room around the developer and to provide an image formation apparatus which includes this developer.
According to one aspect of the present invention, there is provided a developer which comprises, a developing material carrier which supplies a developing material which is contained in a casing, to an image carrier, a high heat conductivity member which has high heat conductivity and which contacts with the developing material, and a radiator which is formed by leading the high heat conductivity member to an outside of the developer.
According to another aspect of the present invention, there is provided an image formation apparatus comprising the above-described developer, wherein an electrostatic latent image is formed on the image carrier by an optical writing unit and visualized as a toner image by the developer, and the toner image is transferred to a recording material.
According to still another aspect of the present invention, there is provided an image formation apparatus comprising a developer which comprises, a developing material carrier which carries and transports a developing material, a developing material container which contains the developing material which is supplied by the developing material carrier, and a developing material stirring and transporting member which stirs the developing material in the developing material container, and which apparatus develops an electrostatic latent image on the image carrier, wherein the image formation apparatus comprises, a heat conductive member which conducts heat accumulated in a bottom of the developing material container to a different position, and a cooling unit which cools the heat conducted by the heat conductive member at the different position. The heat accumulated in the bottom of the developing material container is conducted by the heat conductive member from the bottom to the different position and the heat conductive member is cooled at the position by the cooling unit. Therefore, even with the layout on which there is no spatial room for the provision of a unit which directly cools the bottom of the developing material container below the developing material container, it is possible to cool the developing material container of the developer.
Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.